南京长江四桥附近长江古河谷沉积层序

根据南京长江四桥附近地质钻孔资料,绘制长江古河谷地质剖面示意图。在3个钻孔采集了年代样品,10个钻孔采集了粒度样品。01号孔在-59.4m深度上河床相圆砾石层中沉积物样品有机质的14C年代为14682±110年,邻近钻孔在-33.1～-33.3m深度上粉细砂中有机质的14C年代为10822±240年。通过对典型钻孔沉积层序及沉积物颗粒级配的分析,得知古河谷充填了3期从粗到细的沉积旋回,约-65m以下深槽中的沉积旋回应是末次盛冰期沉积,约-65m～-35m的应是晚冰期沉积,约-35m以上是全新世以来的沉积。

SEDIMENTARY SEQUENCES OF THE YANGTZE RIVER PALEO-VALLEY NEAR THE NO.4 NANJING YANGTZE RIVER BRIDGE SINCE LGMA

The sedimentary sequence near the No.4 Nangjing Yangtze River Bridge investigated. The Paleo-valley depositional sequence was established using bore hole data and geological mapping software. Sedimentary samples for ~14 C age determinatio and grain size analysis were collected respectively, from 3 drill cores and 10 drill cores near the No.4 Bridge. The sedimentary samples at -59.33m deep from drill core 01 gave a ~ 14 C age of is 14 682±110 aB.P., and those at -33.1~33.3 m from the drill cores 02 and 03 gave a ~ 14 C age of 10 822±240 aB.P. Analysis of sedimentary sequences and distribution of the representative drill cores shows that there are three sedimentary cycles in the paleo-valley. The first sedimentary cycle at -65~-90 m deep was deposited in the Last Glacial Maximum, this sedimentary cycle consists of in stratigraphically ascending order pebble gravel, gravel sand, coarse sand and medium sand. The second cycle at -65~-35 m deep was deposited in the Late Glacial Period. It consists of, in asceding order, pebble and gravel, gravel sand, coarse and medium sand, fine sand, and fine and powdery sand. The third cycle among from -35m to top was deposited in the Holocene, consisting of, in ascending order, fine sand, silty sand, muddy clay, and sandy clay.